Steam—Engine



, immediate part.

I UNITED STATES PATENT -OFFICE.

NIKOLA TESLA, on NEW YORK, N. Y.

STEAM-ENGINE.

SPECIFICATION forming part of Letters Patent No. 517,900, dated April10, 1894..

Application filed December 29, 1893- Serial No. 7 N mo To aZZ whom itmay concern.-

Be it known that I, NIKOLA TESLA, a citizen of the United States,residing at New York, n the county and State of New York, have inventedcertain new and useful Improvements in Steam-Engines, of which thefollowing 1s a specification, reference being had to the drawingsaccompanying and forming a part of the same.

lleretofore, engines, operated by the application of a force such as theelastic tension of steam or a gas under pressure, have been providedwith a fly-Wheel, or some rotary system equ1valent in its eifect andpossessing relatively great mechanical inertia, which was relied uponfor maintaininga uniform speed. I have produced however, an engine whichwithout such appurtenances. produces, under very wlde variations ofpressure, load, and other disturbing causes, an oscillating movement ofconstant period, and have shown and described thesame in an applicationfiled on August 19, 1893, Serial No. 483,563. A description of theprinciple of the construction and mode of operation of this device isnecessary to an understanding of my present invention. When a springwhich possesses a sensible inertia is brought under tension as by beingstretched and then freed, it will perform vibrations which areisochronous and, as to period, mainly dependent upon the rigidity of thespring and its'own inertia or that of the moving system of which itforms an This is known to be true in all cases where the force whichtends to bring the spring or movable system into a given position isproportionate to the displacement. In utilizing this principle for thepurpose of producing reciprocating movement of a constant period, Iemploy the energy'of steam orgas under pressure, acting through propermechanism,to maintain in oscillation a piston, and connect with or causeto act upon such piston a spring, preferably, an air spring, under suchconditions as to automatically regulate the period of the vibration, sothat the alternate impulses of the power impelled piston and the naturalvibrations of the spring shall always correspond in direction andcoincide in time. In such an apparatus it being essential that theinertia of the moving system and the rigidity of the spring should bearcertain definite relations, it is obvious that the practicable amount ofwork performed by the engine, when this involves the overcoming ofinertia is'a limitation to the applicability of the engine. I thereforepropose, in order to secure all the advantages of such performances asthis form of engine is capable of, to utilize it as the means ofcontrolling the admission and exhaust of steam or gas under pressure inother engines generally, but more especially those forms of engine inwhich the piston is free to reciprocate, or in other words, is notconnected Witha fly wheel or other like device for regulating orcontrolling its speed. The drawings hereto annexed illustrate devices bymeans of which the invention may be carried out, Figure 1 being acentral vertical section of an engine embodying my invention, and Fig. 2a similar view of a modification of the same,

Referring to Fig. 1,A designatesa cylinder containing a reciprocatingpiston B secured to a rod 0 extending through one or both cylinderheads. 7

D D are steam ducts communicating with the cylinder at or near its endsand E is the exhaust chamber or passage located between the steam ports;The piston Bis provided with the'usual passages F F which by themovements of the piston are brought alternately into communication withthe exhaust port. a

G designates a slidevalve which when re- ,ciprocated admits the steam orthe gas by which the engine is driven, from the pipe G through the ductsD D to the ends of the cylinder.

The parts thus described may be considered as exemplifying any cylinder,piston and slide valve with the proper ports controlled thereby, but theslide valve instead of being dependent for its movement upon the pistonB is connected in any manner so as to be reciprocated by the piston rodof a small engine of constant period,'constructed substantially asfollows :a is the cylinder, in which works the piston b. An inlet pipe 0passes through the side of the cylinder at the middle portion of thesame. The cylinder exhausts through ports 01 (1 into a chamber 01'provided with an opening r The piston 12 is provided with .twocircumferential grooves e, f which communicate through openings gin thesame with the cylinder chambers on opposite sides of the piston. Thespecial construction of this/device may be varied considerably, but itis desirable that all the ports, and more particularly, the exhaustports be made larger than is usually done, so that no force due to theaction of the steam or compressed air in the chambers will tend toretard or accelerate the movement of the piston in either direction. Thepiston 12 is secured to a rod h which extends through the cylinderheads, the lower end carrying the slide valve above described and theupper end having secured to it a plungerj in a cylinder 1' fixed to thecylinder at and in line with it. The cylinder 1' is without ports of anykind and is air-tight except that leakage may occur around the pistonrod which does not require to be very close fitting, and constitutes anordinary form of air spring.

If steam or a gas under pressure be admitted through the port a toeither side of the piston b, the latter, as will be understood, may bemaintained in reciprocation, and it is free to move, in the sense thatits movement in either direction ceases only when the force tending toimpel it and the momentum which it has acquired are counterbalanced bythe increasing pressure of the steam in that end of the cylinder towardwhich it is moving, and as in its movement the piston has shut oil": ata given point, the pressure that impelled it and established thepressure that tends to return it, it is then impelled in the oppositedirection, and this action is continued as long as the requisitepressure is applied. The movements of the piston compress and raret'ythe air in the cylinder 2' at opposite ends of the same alternately, andthis results in the heating of the cylinder. But since a variation ofthe temperature of the air in the chamber would affect the rigidity ofthe air spring,I maintain the temperature uniform as by surrounding thecylinder '5 with a jacket a which is open to the air and filled withwater.

In-such an engine as that just above described the normal pressure willproduce a stroke of determined length, which may be increased ordiminished according to the increase of pressure above or the reductionof pressure below the normal and due allowance is made in constructingthe engine for a variation in the length of stroke. The rate or periodof reciprocation of the piston, however, is no more dependent upon thepressure ap plied to drive it, than would be the period of oscillationof a pendulum permanently maintained in vibration, upon the force whichperiodically impels it, the effect of variations in such force beingmerely to produce corresponding variations in the length of stroke oramplitude of vibration respectively. The period is mainly determined bythe rigidity of the air spring and the inertia of the moving system andI may therefore secure any period of oscillation within very wide limitsby properly proportioning these factors, as by varying the dimensions ofthe air chamber which may be equivalent to varying the rigidity of thespring, or by adjusting the weight of the moving parts. This latter isreadily accomplished by making provision for the attachment to thepiston rod of one or more weights h. Since the only work which the smallengine has to perform is the reciprocation of the valve attached to thepiston rod, its load is substantially uniform and its period by reasonof its construction will be constant. lVhatever may be the load on themain engine therefore the steam is admitted to the cylinder at definedintervals, and thus any tendency to a change of the period of vibrationin the main engine is overcome.

The control of the main engine by the engine of constant period may beeffected in other ways-0t which Fig. 2 will serve as an illustration. Inthis case the piston of the controlling engine constitutes the slidevalve of the main engine, so that the latter may be considered asoperated by the exhaust of the former. In the figure I have shown twocylinders A A placed end to end with a piston B and B in each. Thecylinder of the controlling engine is formed by or in the casingintermediate to the two main cylinders but in allotheressentialrespectstheconstruction and mode of operation of the controlling engine remainsas described in connection with Fig. 1. The exhaust ports at cl however,constitute the inlet ports of the cylinders A A and the exhaust of thelatter is eitected through the ports m, m which are controlled by thepistons B and B respectively. The inlet port for the admission of thesteam to the controlling engine is similar to that in Fig. 1 and isindicated by the dotted circle at the center of the piston b.

An engine of the kind described possesses many and important advantages.A much more perfect regulation and uniformity of action is secured,while the engine is simple and its weight for a given capacity is verygreatly reduced. The reciprocating movement of the piston may beconverted, by the ordinary mechanisms into rotary motion or it may beutilized and applied in any other manner desired, either directly orindirectly.

In another application of even date herewith I have shown and describedtwo reciprocating engines combined in such manner that the movement oroperation of one is dependent upon and controlled by the other. In thepresent case, however, the controlling engine is not designed noradapted to perform other work than the regulation of the period of theother, and it is moreover an engine of defined character which has thecapability of an oscillating movement of constant period.

WVhat I claim is- 1. The combination with the cylinder and reciprocatingpiston and controlling valve of an engine adapted to be operated bysteam or a gas under pressure of an independently ICC IIO

controlled engine of constant period operat: ing the said valve, asdescribed.

2. The combination of an engine cylinder, a piston adapted toreciprocate therein, a slide valve for controlling the admission ofsteam to said cylinder, and an independently controlled engine ofconstant period operatively connected with said valve.

3. The combination with the cylinder, piston and valve mechanism of amain or Working engine, of an independent controlling engine comprisinga cylinder, a piston connected with-the valve mechanism of the mainengine, and a spring acting upon the said piston and controlling theperiod of its reciprocation, as set forth.

4c. The combination with a cylinder and a piston adapted to bereciprocated by steam or a gas under pressure of a cylinder. and a 20plunger therein reciprocated by the piston and constituting with itscylinder an air spring, and an open jacket or receptacle around the saidcylinder and containlng water to preserve the temperature of the anspring uniform, as set forth.

5. The combination with a cylinder, a reciprocating piston and valvemechanism for controlling the admission and .exhaustof the steam or gasunder pressure, 'of a cylinder, a piston connected with and operatingsaid valve mechanism, and an air spring vibrated by the piston, thespring and piston belng related in substantially the manner described toproduce a reciprocating movementof constant period. t

NIKOLA TESLA.

Witnesses:

ARTHUR H. SMITH, ERNEST HOPKINSON.

